ENDURO STAINLESS ALLOYS
ENDURO S— Chromium 13%, carbon under .12%. Suit-
able for applications where moderate corrosion resistance
combined with high strength and toughness are required.
Oxidation resistance to 1500° F.
ENDURO FC— Similar to "S" but with free machining
ENDURO AA— Chromium 17%, carbon under .10%. For
applications where corrosion resistance is more important
than high strength or toughness. Good bending and form-
ing qualities. Oxidation resistance to 1600° F.
ENDURO KA2— Chromium 18%, nickel 8%, carbon under
.16%. Excellent general corrosion resistance to atmos-
•here, salt air, food and dairy products, nitric acid, etc.
High ductility and best drawing qualities. Oxidation resis-
tance to 1600° F.
ENDURO KA2S— Similar i KA2," but with carbon under
.07%. For applications requiring high physical properties
above 1000° F. and for welded fabrication where subsequent
heat treatment is not possible.
ENDURO KA2B— Similar to "KA2/' but with added sili-
con. Oxidation resistance to 1700° F.
ENDURO KA2Mo— Similar to "KA2" but with 3% mo-
ENDURO HC— Ch mum 28%, carbon under .20%. De-
igi 1 for oxidation ance to 2100° F., where great
•ngth and toughness are not required. High resistance
to sulphur and sulphur ga^es, hot or cold.
I NDURO HCN— Chromium 23%, nickel 12%, carbon
i !er .20%. Oxidation resistance to 2100° F., \ h physical
] gher than "KA2S."
ENDURO KNC-3— Chromium 25%, nickel 217c, carbon
under .25%. For applications requiring highest strength and
nidation resistance at highest temperatures.
NDURO KA2. KA2S KA2B, KA2Mo, HCX and KNC-3
are produced undtr Krup] a patents.
OST present or prospective users
of stainless alloys have at some
time been conscious of a lack of accurate basi<
information which would permit them to select
intelligently and to fabricate successfully the par-
ticular type of stainless best suited to a »i\en re-
quirement. Obviously, no single type can meet all
conditions of corrosion and temperature. A series of
booklets has therefore been prepared to supply thi
e\;iet information on the Enduro Stainless Irons.
Stainless Iron generally is an allo\ of iron and
chromium, or of iron, chromium and nickel, with
ver\ low carbon content. The stainless properties
of the alloy are due to the ability of chromium to
form with iron a solid solution which is resistant
to the various corrosi\e media. It is essential that
sufficient chromium be present in solid solution t<.
ensure stainless properties. The chromium con-
tents of Enduro Stainless Irons have been adjusted
Stainless irons as a class do n<>l respond to hard-
ening 1»\ heal treatment. Neither do the} require
special heal lieatment other than thai received al
the mill to develop stainless properties. Stainless
irons a- a class lend themselves to deep drawing and
other forming operations.
There is a distinction between stainless iron and
stainless steel, though the latter term is popularly
if erroneously used lo desj^nale all stainless alloys
StrietU speaking stainless steel is an alloj of iron,
chromium and carbon. The amounl of carbon i
Mich that the material harden* upon quenching.
This branch of the stainless family is suitable for
cutlery and applications where high physical prop-
erties, hardness and wear resistance are required,
but does not lend itself to deep drawing or forming.
Not only does stainless steel require very careful Selection of Type and Finish — Enduro
polishing, but it must also be carefully heat treated
before polishing to develop its corrosion-resisting
Types of Enduro Stainless — To meet the de-
mands of industry for corrosion- resisting alloys
suitable for a wide variety of specific purposes, the
Enduro Stainless Irons have been developed in a
number of types. In this development all factor-
ail ting corrosion resistance have been considered
nd their relative importance established. The
esult is a series of alloys possessing maximum
corrosion resistance and physical properties, con-
sistent with ease of workability, for each field of
ipplication. ll is noteworthy that this has been
accomplished without undul) increasing the cosl
of I he alloys.
Stainless Irons are furnished in several different
finishes. The finish of the stock used will depend
on the amount of forming necessary. Jt is inadvis-
able to use polished sheets for extra deep drawing
operations where score marks from dies are likeh
to occur in forming or where it is necessary l<. re-
anneal to make a second drawing operation. An
unpolished, fully annealed and pickled sheet
designated as our number one (1) finish should be
used. Polished finish should he used onl\ where
stock will be employed without further working
or where the degree of working is small.
Much harm has been
done by exaggerated claims of corrosion resistance.
Metals and alloys are resistant to corrosion in
erent degree, none being entirely proof against
all corrosive agent-. Each melal or allo\ is limited
as to the field in which ii is serviceably resistant;
hence while it may possess excellent resistance in
its field, it by no means follows that it will be
equally resistant to all attacking media under all
To simplify this problem we group the application
of l he Enduro Stainless Irons under three headings:
1 . Atmospheric Corrosion — understood t«»
mean exposure to weather conditions.
2. Wet Corrosion — understood to mean
partial or total immersion in corrosive
:5 . Dr\ Corrosion — understood to mean seal-
ing at elevated temperatures.
Atmospheric Corrosion — In this field the
Enduro Stainless Irons are excelled by no other
stainless alloys. The higher the allo\ content of
each Enduro type, the more resistant I he alloy is
to corrosion by weather exposure. In addition to
this result from higher content of alloys, the form-
ing and deep drawing qualities also are favorabh
influenced, particularly b> the addition of nickel.
Ml types of Enduro Stainless Irons produced b\
Republic Steel Corporation are suitable for general
resistance to atmospheric corrosion.
Wet Corrosion — Enduro Stainless Irons are
resistant to nitric acid and similar oxidizing agents.
to sulphur and sulphur compounds and to the more
common organic acids occurring in the household.
They are not resistant to hydrochloric or sulphuric
acids except under special conditions.
The rate at which corrosion (solution of the allo>
in the corrosive liquid) takes place depends upon
a number of factors, among which are the con-
centration of the other elements in the solution and
the character of the solvent; the temperature; the
^late of the solution, whether agitated or at rest;
the amount of dissolved oxygen or other oxidizing
agents present; the presence of impurities in the
solution which might act as inhibitors, or them-
selves attack; electrolytic action because of contact
with other metals, etc.
Since these and other factors affect the rate at
which corrosion takes place, it is questionable
whether laboratory tests on the stainless irons are
of great practical value except insofar as the> in-
dicate whether attack does or does not take place
and if it does, whether rapidly or slowly. Tests on
samples of Knduro Stainless Irons under actual
conditions are much preferable to calculations of
probable corrosion rate based on laboratory data.
The Republic Steel Corporation has a large amount
of corrosion data obtained from bests in pun
solutions and also from actual application of Ih
various alloys under service conditions. If the pro-
spective user of Enduro Stainless will submit the
application to our metallurgical department a
recommendation will be made.
Dry Corrosion — Enduro Stainless Irons are
resistant to scaling at elevated temperatures. Each
type is best suited for certain conditions and tem-
peratures. All Enduro Stainless [rons are resistant
to sulphur gases up to 1000°F.
In dealing with the application of Knduro Stainless
Irons to high temperature service it is important
to differentiate between intermittent and contin-
uous service. This is necessary because >me of the
stainless alloys have a tendency to cast ofF their
protective scale when alternately healed and cooled.
due to difference in the coefficient of expansion
between the scale and the metal itself. There ha>
been established a maximum temperature foi
these service conditions which is given for each
t \ pe of nduro.
Physical Properties at High Temperatures
\ selecting a material for the
design of equipment which is to
be used under high temperature conditions, where
high stresses ma\ he encountered, as in oil refiners
operations, the following qualifications are neces-
(;«) The metal must have tin* requisite strength at the
sprrilh'd lemperal ure.
(\>) l\ must not oxidize under ihe action of tin- Name or
(c) 1 1 iim-i noi heroine brittle while in service.
(d) It must n isl Lhe corrosive action of the materials with
v\ hich it is in conl u I -urh us liquids, pases, etc
Enduro on th« Chryvl«r Tc
I ' I e 1 1 * t r e r \i I m- i a r i I \ d «
MM! | r li 'lli| || K*s Ih.l L|
.1 illy * il h the rati tt w hi* h in plied.
But when the test is made at high temperatures
the rate of pulling of the tensile lest piece has a
marked effect on the ultimate tensile strength
obtained. The more slowly t lie test piece is pulled,
the lower is the strength shown by it- It is thus
apparent that the tensile strengths of metals at high
temperatures as ordinarily determined by short-lime
tests cannot be used tor design purposes. It is
equally evident that the effect of stress on the metal
held ai a high temperature for a long time must he
known before it is possible intelligently to design
equipment to be used under- such conditions.
I f the strength of a meial at a given high temper-
ature is determined onl> b> ordinary tensile tests.
piece of equipment subjected to that temperature
lor i longer time, under pressure, using a safe liber
Lress as determined l>> ihe short-time tests, will
pr< -i\el\ stretch, or "creep." This will con-
tinue until a point is reached where the metal
thickness becomes so greath reduced thai the
pressure can no longer be withstood, and the ap-
paratus will fail.
li is well to note thai this reduction in the thickness
of the metal ma> also be hastened b> the effects of
rrosion n of oxidation, or a combination of both
In order to design apparal us or equipment suitable
for service at various H«-\ aicd temperatures, when
stn i - will be high, il is necessary to determine the
• reep strength* 1 of the metal. The "creep strength"
i a given temperature ma) therefore be defined
as ih« tress .ii which the metal will elongate r,
during 1 00, 00 n or lu.noo I - ad that temperature
The n ep strength* 4 of ea<-h Knduro type,
mpared to plain carbon steel in given in com
pai m undei i h i ype. In applying this data i
problems of practical design Jes should be | <|
correspond ii to the highest temperatures an-
i ieipated i i fai o»r of -;dei \ iDtrodu< ed to prevent
d- 4 1 s being em ceded, should the temperature
l< ri I all \ be in
A Few of the Polishing Machines in Republic's Finishing Division
Preparation of Surface Polishing
HE preparation of the surface to
be exposed to corrosive attack is
of the utmost importance. When the highest degree
of corrosion resistance is desired, the scale resulting
from hot working must be removed and the surface
ground and polished.
To secure the permanent, beautiful, silver-white
lustre characteristic of Enduro Stainless Irons,
which permits them io replace such materials as
nickel plate, chromium plate, nickel silver, tinned
copper, and the copper nickel alloys, it is necessary
that certain precautions be observed. Polishing
and buffing equipment which has been used for
polishing other metals should have all such metal
particles carefully removed before use in polishing
Enduro. Careful selection of polishing grits and
buffing compounds is necessary to insure their
freedom from iron, as otherwise such iron ma> be
worked into or remain on the surface of the polished
article and will under corrosive conditions give the
erroneous impression thai the stainless alloy i^
V factor of equal importance is that all surface
imperfections must be removed to secure maximum
corrosion resistance. In polishing flat surfaces it
is necessary to begin operations with coarser grits
than when polishing formed articles. The rule
should be to use the finest abrasive possible and
yel remove all of the surface imperfections, the
that coarse grit marks are verv
than (hat of polishing, 7200 to 12000 lineal feet per
difficult to remove.
A polishing speed of from 5000 to 7000 lineal feet
per minute is productive of very good results. The
first few polishing operations may be done dr> . but
the final operation should be done on greased
wheels. Care must be exercised not to burn the
work, the lower coefficient of thermal conductivity
making this danger greater than when polishing
copper, brass or steel.
The bulling of Enduro Stainless Irons must be done
with iron-free bufling compound. This precludes
the use of ordinary jeweler's rouge. Green chrome
oxide is a suitable material where a mirror finish
is not necessary; however, when such a finish i-
necessary special buffing ((impounds are required
followed by the use of chromium oxide to bring out
the color. The speed of bufling should be higher
As regards polishing, the character of the finish of
the exposed surface is the most important factor
in producing resistance to stain and tarnishing;
hence, the more perfect the finish, the less the like-
lihood that the metal will slain.
When formed articles do not require maximum
resistance to corrosion and are to be used in I lie
"as drawn" or semi-polished condition, it is recom-
mended that the article be given a passivation or
When using stainless iron in the semi-polished con-
dition there will usualW be some 4 discoloration of
the exposed surface. This eventually develops
into a permanent, tightly adherent surface coating
which, if appearance is not a primary consideration?
does not adversely affect the life of the metal.
Passivation of Enduro Stainless Alloys
Polished sheets as furnished for exposure to weather
conditions are given a special surface treatment
before shipment from Republic Steel Corporation,
This treatment is known as a "Passivation Treat-
ment and insures proper resistance to corrosion,
staining, and discoloration.
In installing such polished sheets on buildings the
fabricator will often find it necessary to cut,
machine, punch, shear, bend, or otherw ise work the
metal with the result that the passivated condition
is destroyed. In forming the sheet the forming tools
It impossible to immerse pieces, all sheared edge
drilled or punched holes, engraved or scratched
surfaces should be swabbed or scrubbed with the
above nitric acid solution.
3. Rinse in clear water to remove all traces of
acid, and dry.
usually are made of regular die steel. There is a
possible abrading action between the stainless metal
and the steel die which may leave a surface film of
iron on the stainless surface after the forming opera-
tion. This film should be removed by the passivating
treatment as otherwise a form of rusting wi
appear after the unit is placed in service. With
certain forming operations it is possible to use
paper or other lubricating compounds between
the stainless metal and the steel die, which will
prevent the abrading action.
Cleaning of Polished Enduro— To keep
polished Enduro surfaces clean, use soap and water,
with a 4 'grease free" drying and polishing cloth.
\\ here necessary to use a polish, Bon Ami is recom-
mended. Do not use liquid metal cleaners, as they
are liable to dull the lustre.
Tile and brick cleaning compounds are likely l<»
contain ingredients which may etch or discolor
Enduro Stainless and il is therefore recommended
that when Enduro is installed in conjunction with
(ile or brick it be wiped with a greasy cloth to
protect the surface when the lile is cleaned.
Contact with Other Metals — The
polished Enduro Stainless sheet and trim on I be
Where this is not possible it is recommended that outside of buildings may necessitate the use of
after such operations the metal surface be repas- steel supports that are welded or otherwise attached
to the stainless metal and then attached to the steel
structure of the building. These points of contact
of steel to stainless should be protected from cor-
rosion as much as possible; a coating of paint is
sivated in I lie following manner;
1. Wash thoroughly in kerosene to remove all
traces of grease, drawing compounds, etc, and
dry by rubbing with whiting.
2. Immerse in a 20% by volume solution of
commercial nitric acid at a temperature of 130°F.
for 20 to 30 minutes. This acid will not attack
ihe metal nor destroy the surface finish. (Tanks
for holding such acids should be lined with stain-
The contact of Enduro Stainless with other metal
should be avoided where electrolytic corrosion i-
apt to occur (wet corrosion). Under all other condi-
tions, it is satisfactory to have Enduro Stainless in
contact with dissimilar metals.
Following are a few of the applications in which the various types of Knduro have met
with conspicuous success.
Enduro K A 2
Canning and preserving equipment.
Cold storage plant apparatus.
Dairy and milk handling machinery.
Dyeing, bleaching and finishing machinery.
Exterior building trim.
Household electrical appliances.
Ice cream freezers and cabinets.
Washing machines and parts.
Meat slicing machine parts.
Packing house equipment.
Paper and pulp machinery.
Electric refrigerator parts.
Soap making machinery.
Soda fountains and counters
Sugar refinerj machinery.
Enduro A A
( andy making machinery.
Canning or preserving equipment
Chemical plant apparatus.
( looking utensils.
( iolf club heads.
Ice making machinery.
Nitric acid planl equipment.
Nitrogen fixation apparatus
Oil refinery equipment.
Pyrometer protection tubes.
Rubber plant machinery.
Tanks — all kinds.
Varnish ket ties.
Automobile parts such as pump shafts, etc
Heater bars for paper mills.
Gage and indicator parts.
Locomotive safety valve seats.
Mining i chiner^ and equipment.
Hitle and revolver barrels.
Pumps or pump parts.
Railroad equipment .
Steam turbine parts.
Shafts for deep well pumps.
Valve parts for high pressure steam, and
oil refinery equipment.
Parts requiring high phvsical proper! ies.
Knduro is available in bars, castings, forcings, plates, sheets, strip, tubing, *ire and
innumerable finished products through fabricators.
REPUBLIC STEEL CORPORATION
Printed in I . S. \.
523 ARCH STREET